The present invention relates to a homogenizing valve.
The present invention refers in particular to equipment for homogenizing fluids and in particular liquids containing particles, globules and fibres, that is, products which are substantially liquid but subject to the formation of solid portions or otherwise liquids which have high density (such as milk containing fat globules).
Homogenizing equipment comprises a high-pressure pump and a homogenizing valve with an inlet connected to the delivery port of the pump for receiving pressurized fluid and an outlet for the low-pressure homogenized fluid.
The homogenization obtained in this way consists substantially of breaking up the globules in order to achieve the following objectives:                to reduce the average size of the globules to the minimum;        to make the globule size as uniform as possible (or, expressed in statistical terms, to reduce the variance of the amplitude distribution of the of the globules in the product treated).        
The fluid is forced through a passage of reduced dimensions, from a first, high-pressure chamber (connected to the pump delivery port) to a second chamber (connected to the valve outlet).
This passage is defined by a passage head forming part of the valve body (and therefore fixed) and an impact head which is mobile axially with respect to the passage head. In effect, the passage consists of a gap between the impact head and the passage head.
The fluid under high pressure in the first chamber presses against the surface of the impact head exerting a pressure on the impact head which tends to widen the passage. The impact head is fitted with a pusher which exerts a force in the axial direction on the impact head in order to counteract the pressure of the fluid.
In this way and by suitably controlling the action of the pusher, it is possible to maintain the width of the passage at a required value which is substantially constant. This force is a function of the values of the operating flow rate and operating pressure of the valve.
The fluid flows through the forced passage from the first to the second chamber losing pressure and, at the same time, accelerating. The acceleration causes fragmentation of the globules in the fluid. An additional, known feature is the fitting of an impact ring in the second chamber designed to intercept the accelerated fluid; the fluid hits the impact ring at high speed thus causing further fragmentation of the globules.
In general it is considered to be good practice to optimise energy use in the homogenization process. The objective here is to obtain, for a particular pressure, the best possible result for homogenizing the fluid in the terms described above.
This is the background to known technical solutions (for example EP810025 by the same applicant) where the first and second chambers have an annular shape such that the high-pressure fluid in the first chamber presses on the impact head on an annular surface of a relatively small size. This has the advantage that it is possible to operate with especially small values of the passage (also known as gap) for a preset amount of energy applied to the equipment. In this way it is possible to drive the fluid at a high speed which is also uniform (that is, applied to the entire volume of fluid processed).
However, this type of technical solution has shortcomings. Not all the globules accelerated actually impact with the impact ring and some of the globules impact with the impact ring at speeds which are too low. Here it should also be noted that not all the fluid globules are accelerated at the same speed. One of the reasons for this is that the width of the passage is not perfectly constant given that the infeed pump has a finite number of pistons with the result that there are oscillations in the volumetric capacity.
WO 97/31706 discloses a homogenizer valve which comprises a pressurized movable valve cone, a valve seat provided with a central flange, a valve housing, and a wear ring. A recess is present between the flange and the wear ring and so the passage for the fluid may have some drawbacks. U.S. Pat. No. 5,217,037 and EP-A-0593833 (this document refers to a previous patent application of the same Applicant) relate to homogenizing valves having the same drawbacks of the prior art.